The invention relates to a method for preparing refractory carbides and, more particularly, to a method for preparing ceramic-matrix composites containing refractory carbides which are particularly well suited for high temperature propulsion applications and the like.
Refractory carbides and composites containing refractory carbides are useful in high temperature, high stress applications, for example in propulsion applications.
Conventional processing for manufacturing refractory carbides requires extremely high temperatures.
Ceramic-matrix composites are particularly desirable for high-temperature applications such as propulsion applications and the like. However, preparation of such composite ceramic materials is difficult, and frequently leads to excess carbon or refractory metal, neither of which is desirable since the excess carbon can cause oxidation problems and excess refractory metals lead to extra weight of the resulting component. Excess refractory metals can also disadvantageously react with common composite reinforcement phases, such as carbon fiber.
It is therefore the primary object of the present invention to provide a method for preparing refractory carbides which can be carried out at lower temperatures than conventionally possible, and which allows preparation of high temperature propulsion components with desirable properties.
It is a further object of the present invention to provide such a method which allows for preparation of refractory carbides at reduced cost.
It is still another object of the present invention to provide a method whereby composite refractory carbide structures are prepared.
Other objects and advantages of the present invention will appear hereinbelow.
In accordance with the present invention, the foregoing objects and advantages have been readily attained.
According to the invention, a method is provided for preparing a refractory carbide component, which method comprises the steps of providing a carbon rich polymer precursor to silicon carbide and excess carbon; determining an amount of excess carbon in said carbon rich polymer precursor; combining said carbon rich polymer precursor with a selected amount of refractory metal to form a precursor/metal mixture, said selected amount being selected so as to provide stoichiometrically equivalent amounts of said excess carbon and said refractory metal; forming said mixture into a preform of a propulsion component; and heating said preform so as to thermally degrade said carbon rich polymer precursor to produce said silicon carbide and said excess carbon, said excess carbon and said refractory metal reacting to form refractory metal carbide and provide said refractory carbide component.
Suitable refractory metals include hafnium, tantalum, titanium, silicon, tungsten, zirconium and mixtures thereof, and the residual carbon generated by thermal degradation of the carbon rich polymer precursor reacts with such refractory metal to provide a final material containing substantial amounts of silicon carbide and other refractory metal carbide.